Paulette Carr on tue 13 nov 01
Greetings to all glaze gurus:
I need some help with a cone 9 (oxidation) Transparent Base glaze. I am=20
attempting to meet the following criteria set forth by Tony Hansen in=20
developing hismid-range Glossy Base Glaze:
(1) reliable
(2) stable
(3) hard surface
(4) transparent
(6) good application properties
(7) a good vehicle for stains/colors
(8) forgiving: not touchy with regard to precise glaze thickness, or=20
precise firing temperature/regimen.
(9) low expansion,=20
(10) adjustable with readily available ingredients.
I have been working with the following cone 9 (ox) Transparent Base glaze:
WOLLASTONITE............. 40.00
PETALITE................. 10.00
G-200 FELDSPAR G200...... 12.50
GROLLEG KAOLIN........... 25.00
FLINT.................... 12.50
=3D=3D=3D=3D=3D=3D=3D=3D=3D
100.00
(+ 1% VeeGum Cer and propylene glycol)
CaO 0.89* 20.60%w 23.11%m
Li2O 0.04* 0.45%w 0.94%m
MgO 0.01* 0.08%w 0.13%m
K2O 0.05* 1.92%w 1.28%m
Na2O 0.02* 0.45%w 0.45%m
TiO2 0.00 0.01%w 0.01%m
Al2O3 0.33 13.79%w 8.51%m
SiO2 2.53 62.52%w 65.48%m
Fe2O3 0.00 0.19%w 0.08%m
Si:Al 7.69
SiB:Al 7.69
Expan 6.97
I am having a problem with crazing, and I want to eliminate this tendency. =20=
I=20
use it on Tucker=E2=80=99s White Sculpture. I can control the crazing by us=
ing a=20
thinner coating of glaze (2-3 brushed coats, rather than 4), but then I run=20
the risk of not getting good, even coverage, since I am brushing it on. I a=
m=20
firing tiles, so my firing is very slow, both in the heating and cooling=20
phases.
I can see from the glaze analysis, and comparison to Cone 9 Glaze limits tha=
t=20
I might be low in silica and alumina... is this the case? I have poured ove=
r=20
the literature, and am quite frankly stuck ... probably because I don=E2=80=
=99t know=20
enough. Since I am very pleased with the color response, I don=E2=80=99t wa=
nt to use=20
Zinc, boron or MgO. =20
My new goal is to learn how to use the glaze calculation programs to predict=
=20
changes to this glaze that may solve the fit problems. As an alternative=20
approach, I will use Ian Currie=E2=80=99s grid, but I would really like to g=
et a=20
handle on the glaze calculation approach, especially if I might be changing=20
the fluxes.
Any nudges you can give me in the right direction would be gratefully=20
appreciated!
My best,
Paulette Carr
St. Louis, MO =20
Ken Chin-Purcell on thu 15 nov 01
Paulette,
> I need some help with a cone 9 (oxidation) Transparent Base glaze.
I fire oxidation with cone 8 down, cone 9 just over (3 o'clock).
My clear has it's origin with Nigel Wood and comes via Ray Aldridge.
As I use it (recalculated for Custer spar):
Flint 18.5
Wollastonite 22.5
EPK Kaolin 14
Custer Feldspar 45
Ray gave it to me using G-200:
Flint 21
Wollastonite 22
EPK Kaolin 13
G-200 Feldspar 44
This is a striaghtforward clear that when not-to-thick is flawless.
It tends to cloud milky when thick. In molecular terms it's 75% Ca
and 25% KNa, which suposedly is about the optimum ratio for melting.
At four ingredients it's the simplest glaze I use. It seems to have a wide
melting range, is high in alumina and silica, and does not run.
It takes stains and cobalt well. 1-2% Copper is jade green, as opposed
to turquoise in a more alkaline glaze. The high calcium bleaches iron,
although I do use it as a base for an iron saturated (10% RIO) glaze that with
some rutile (1%) and ilmenite (1%) has some nice speckles (IMHO).
I only use dipping to apply. Perhaps someone else can recomend an
additive to make it brush on nicely - whatever the commercial underglazes
use.
Another cone 9 ox clear that does craze (but in a nice way) is Takeshi Yatsuda's
base glaze. This comes from my stay in Ireland (Takeshi teaches in Belfast)
and I have *not* tried it yet with US ingredients:
Potash spar 20 (I used FFF spar)
Neph Syn 15
Whiting 20
Talc 10
China Clay 15
Flint 15
Bone Ash 2
That lovely cream of his is the above with 0.3% manganse and 1.5% RIO.
Let me know if I can be any more help.
-- Ken Chin-Purcell
Lawrence Ewing on thu 15 nov 01
Hi Paulette,
On the Matrix web site you will find a tutorial which discusses =
manipuation of glazes to adjust crazing. =20
MATRIX TUTORIALS:=20
http://www.Matrix2000.co.nz/MatrixTutorials
The tutorial discusses issues which effect crazing and uses a sample =
glaze to go through the process of changing a glaze using Matrix (same =
principles apply for any calculation software)
Cheers,
Lawrence Ewing
Senior Lecturer
Ceramics Department
School of Art
Otago Polytechnic
Dunedin
New Zealand
email: lewing@clear.net.nz
phone +64 03 472 8801
MATRIX GLAZE CALCULATION SOFTWARE:=20
http://www.Matrix2000.co.nz
GLAZETEACH:=20
http://www.Matrix2000.co.nz/GlazeTeach
MATRIX TUTORIALS:=20
http://www.Matrix2000.co.nz/MatrixTutorials
MATRIX ADDITIONAL MATERIALS RESOURCE: =
http://www.Matrix2000.co.nz/MatrialsWeb/default.htm
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]On
Behalf Of Paulette Carr
Sent: Wednesday, November 14, 2001 4:18 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Need help with cone 9 oxidation glaze
Greetings to all glaze gurus:
I need some help with a cone 9 (oxidation) Transparent Base glaze. I am =
attempting to meet the following criteria set forth by Tony Hansen in=20
developing hismid-range Glossy Base Glaze:
(1) reliable
(2) stable
(3) hard surface
(4) transparent
(6) good application properties
(7) a good vehicle for stains/colors
(8) forgiving: not touchy with regard to precise glaze thickness, =
or=20
precise firing temperature/regimen.
(9) low expansion,=20
(10) adjustable with readily available ingredients.
I have been working with the following cone 9 (ox) Transparent Base =
glaze:
WOLLASTONITE............. 40.00
PETALITE................. 10.00
G-200 FELDSPAR G200...... 12.50
GROLLEG KAOLIN........... 25.00
FLINT.................... 12.50
=3D=3D=3D=3D=3D=3D=3D=3D=3D
100.00
(+ 1% VeeGum Cer and propylene glycol)
CaO 0.89* 20.60%w 23.11%m
Li2O 0.04* 0.45%w 0.94%m
MgO 0.01* 0.08%w 0.13%m
K2O 0.05* 1.92%w 1.28%m
Na2O 0.02* 0.45%w 0.45%m
TiO2 0.00 0.01%w 0.01%m
Al2O3 0.33 13.79%w 8.51%m
SiO2 2.53 62.52%w 65.48%m
Fe2O3 0.00 0.19%w 0.08%m
Si:Al 7.69
SiB:Al 7.69
Expan 6.97
I am having a problem with crazing, and I want to eliminate this =
tendency. I=20
use it on Tucker=E2=80=99s White Sculpture. I can control the crazing =
by using a=20
thinner coating of glaze (2-3 brushed coats, rather than 4), but then I =
run=20
the risk of not getting good, even coverage, since I am brushing it on. =
I am=20
firing tiles, so my firing is very slow, both in the heating and cooling =
phases.
I can see from the glaze analysis, and comparison to Cone 9 Glaze limits =
that=20
I might be low in silica and alumina... is this the case? I have poured =
over=20
the literature, and am quite frankly stuck ... probably because I =
don=E2=80=99t know=20
enough. Since I am very pleased with the color response, I =
don=E2=80=99t want to use=20
Zinc, boron or MgO. =20
My new goal is to learn how to use the glaze calculation programs to =
predict=20
changes to this glaze that may solve the fit problems. As an =
alternative=20
approach, I will use Ian Currie=E2=80=99s grid, but I would really like =
to get a=20
handle on the glaze calculation approach, especially if I might be =
changing=20
the fluxes.
Any nudges you can give me in the right direction would be gratefully=20
appreciated!
My best,
Paulette Carr
St. Louis, MO =20
_________________________________________________________________________=
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